Material handling apparatus



Dec. 24, 1957 w. w. CHEW 2,817,792

MATERIAL HANDLING APPARATUS FiledJan. 11, 1956 37 39 IN V EN TOR.

WILSON w. CHEW BY A FIG. a FIG. 4 j

ATTORN EYS United States Patent "ice 2,817,792 MATERIAL HANDLING APPARATUS Wilson W. Chew, Barrington, R. I., assignor to Production Plastics Corporation, a corporation of Rhode Island Application January 11, 1956, Serial No. 558,441

7 Claims. (Cl. 317-2) This invention relates to a material handling apparatus, such for instance as a fork lift truck, which is designed for picking up pallets loaded with work or for various other purposes.

Heretofore in the use of material handling apparatuses which were used in the handling of hazardous work, such as gasoline or explosives where the steel fork of a lift truck sliding on a concrete floor or its striking a hard object like a concrete column might produce a spark, it has been customary to cast the lifting fork of bronze or some material high in copper content so that sparks will not jump from the fork to some ground which might cause an explosion if this occurred in an area where gasoline fumes or other explosive mixtures existed. The cost of solid bronze forks was rather high compared to a steel fork.

One of the objects of this invention is to provide a lifting fork which will be non-sparking and of materials which will reduce the cost from what has had to be heretofore used.

Another object of the invention is to utilize a steel fork which will have minimum dimensions and yet the strength required and to provide a covering of minimum thickness over this steel fork to prevent sparking from the fork when the same touches a floor or some other point which may act as a ground and to which static electricity may discharge.

Another object of the invention is to coat the arms largely with a non-metallic material such as Fiberglas and a resin from which sparks will not be transmitted.

Another object of the invention is to coat the heel and toe portions with a non-sparking metal but the intermediate and longer portions of the fork arms with a nonmetallic non-sparking material.

With these and other objects in view, the invention consists of certain novel features of construction as will be i more fully described and particularly pointed out in the appended claims.

In the accompanying drawings:

Figure 1 is a perspective view of a fork lift truck incorporating my invention;

Figure 2 is a sectional view taken longitudinally through one of the arms of the fork;

Figure 3 is a section on line 33 of Figure 2;

Figure 4 is a section on line 4--4 of Figure 2;

Figure 5 is a perspective view of a fragmental portion of the arm showing the non-metallic material in the step of being wrapped about one of the fork arms.

With reference to the drawings, designates generally a so-called fork lift truck with Wheels 11 and 12 with mechanism to drive the rear wheels and steer the front ones by the guiding wheel 13. Elevating mechanism is designated as at 14 which comprises guides 15 for a carriage 16 upon which the forks 17 are fixed. These forks comprise a pair of arms 1818 having vertical portions 19 and horizontal portions 20. At the juncture of the vertical and horizontal portions 19 and 20 there is a right angle bend or heel 21, while the tips or toes of the arms 2,817,7 92 Fatented Dec. 24, 1957 are designated 22. These forks and arms if formed wholly of steel or iron, cause sparks to readily jump from these arms to a ground due to the picking up of static electricity or from contacting with a rough floor from abrasion and may cause a spark to be transmitted between the steel arms and the ground.

In order to provide protection against such sparking, Ibraze at the heel portions 21 acoating which is largely of copper as at 23 which completelyenvelopes theheel along a portion of the vertical part 19 and a part of the horizontal part 20 so that the heel is completely coated with this bronze material, while at the toe there is a similar coating of bronze 24 which extends over the end of the toe and back along the toe for a short distance, as shown more clearly in Figure 1. This is also applied by brazing. The ends of the brazing along the horizontal arm 20 are at generally right angles to the length and form shoulders 25 and 26.

Between these shoulders 25 and 26 and over the arm 20 I wrap a sheet of woven yarns comprising glass that has been melted and drawn into fine fibers which are twisted and plied. This is known by the trade name Fiberglas. Such a sheet is precut to substantially fit the core 27 which it is to embrace so that it will meet at a juncture line 28 extending generally longitudinally of the arm. To hold this Fiberglas in place, there is a polyester resin which is applied as a liquid over the surface of this woven Fiberglas which serves to bond the edges together and also to bond the Fiberglas to the steel core 27, thus holding it firmly in position.

I find that by treating a fork arm in this manner, when the same slides on a concrete floor or strikes a concrete column, any electricity will be transferred from the fork through either the heel or toe portion to the ground and no spark will be produced, the non-metallic material serving as an insulation between these portions, while sparks will not jump from the insulation nor will they jump from the copper clad portions of the arms. This manner of treating permits great strength to be had with minimum dimension and weight because of the strength of the steel used in the fork, while the copper and non-metallic coating serve to prevent sparks from jumping from the fork to a ground.

I claim:

1. In a material handling apparatus, a fork having horizontal arms for engaging the work with heel and toe portions, comprising a core of a material from which sparks may jump, a coating of a metal largely copper at the heel and toe portions, and a coating of a non-metallic material from which sparks will not jump between said coated heel and toe portions to complete the coating therebetween and cover the horizontal portion of the forks.

2. In a material handling apparatus as set forth in claim 1 wherein the non-metallic material is a sheet of material comprising intermeshing glass yarns.

3. In a material handling apparatus as set forth in claim 1 wherein the non-metallic material is a sheet of material comprising intermeshing glass yarns bonded with a polyester resin.

4. In a material handling apparatus as set forth in claim 1 wherein the non-metallic material is a sheet of material comprising intermeshing glass yarns of sheet form Wrapped about the arms of the fork and bonded with a polyester resin.

5. In a material handling apparatus as set forth in claim 1 wherein the non-metallic material is a sheet of material comprising intermeshing glass yarns in woven form wrapped individually about the arms of the fork and bonded in place with a polyester resin.

6. In a material handling apparatus, a fork having horizontal arms for engaging the work, comprising a core of a material from which sparks may jump, a coating of a metal largely copper over a limited portion at one end of the horizontal portion of the arms, and a coating of non-metallic material from which sparks Will not jump over a major portion of the arms and adjacent the metal coating to complete the coating of the arms of the fork.

7. In a material handling apparatus, a fork having horizontal arms for engaging the work with toe portions, comprising a core of a material from which sparks may jump, a coating of metal largely copper over the toe portions, and a coating of non-metallic material from which sparks will not jump extending from the metal coating at the toe portions to complete the coating of the arms.

References Cited in the file of this patent UNITED STATES PATENTS Wilkofi June 11, 1940 Merrill Nov. 18, 1941 Ward et a1. May 13, 1952 Burgin Aug. 17, 1954 Momyer Feb. 15, 1955 Price May 8, 1956 

